Readily cleaned burner

ABSTRACT

A liquid fuel burner having a combustion pot with perforated sides and a constant level feed valve connected to the pot by a feed pipe, and a radial access passage with a removable cover arranged to allow passage of a cleaning tool for scraping the pot bottom and for removing debris removed from the bottom, the lower edge of the access passage being in direct proximity to the bottom.

United States Patent Inventor Jean-JacquesCamps 8 Rue Jean-.laures, l0Nogent-Sur-Seine, France Appl. No. 778,268 Filed Nov. 22, 1968 PatentedJune 8, 1971 Priority Nov. 27, 1967, Sept. 17, 1968 France 129,719 and166,417

READILY CLEANED BURNER 23 Claims, 14 Drawing Figs.

US. Cl 431/338 Int. Cl F23d 3/02 Field of Search 431/338, 331, 3 33, 339 [56] References Cited UNITED STATES PATENTS 2,473,653 6/1949 Little6. 431/338 3,017,923 [/1962 Jensen et a1. .1 431/339X 3,304,984 2/1967Hellmann 431/331 FOREIGN PATENTS 1,102,706 5/1955 France 431/339 762,54411/1956 Great Britain 431/333 Primary ExaminerEdward G. Favors Anorney-Young and Thompson ABSTRACT: A liquid fuel burner having a combustionpot with perforated sides and a constant level feed valv connected tothe pot by a feed pipe, and a radial access passage with a removablecover arranged to allow passage of a cleaning tool for scraping the potbottom and for removing debris removed from the bottom, the lower edgeof the access passage being in direct proximity to the bottom.

PATENTED JUN 8197i SHEET 1 BF 5 FIG.5

Nil

6v YJM Hrrys.

PATENTEU JUN 8 1971 SHEET 2 BF 5 FIG.6

daqw- (/qcauar 64/;

PATENTED JUN 8 I971 SHEET 3 BF 5 Has Away/rm Y/LMW PATENTEU JUN 8 :97:

mg I

JEAN J; c005: CAMPJ 6 Y y (7% %l7 firryj,

READILY CLEANED BURNER BACKGROUND OF THE INVENTION 1. Field oftheInvention This invention relates to liquid fuel heating appliances ofthe kind comprising a vaporizing burner. Such a burner comprises acylindrical combustion pot having a perforated wall, in combination witha feed valve of the constant level-type arranged to limit the volume ofliquid fuel allowed to enter the base of the pot.

2. Description of the Prior Art The known appliances of this kind have aseries of drawbacks affecting their conditions of use, by forcing upontheir users onerous and soiling maintenance work, and without protectingthem against combustions which are occasionally dangerous and at allevents likely to cause production of soot injurious to the surroundingsof the appliance.

in the known appliances it is practically impossible after a certainperiod of operation, to prevent the formation in the bottom of thecombustion pot of a solid crust resulting from the accumulationof'combustion wastes or cokes which eventually clog the fuel inlet andinterfere with the normal operation of the gasifying or vaproizingprocess at the bottom of the combustion pot. It is and remains essentialto undertake a cleaning action for removal ofthese wastes, from time totime. To this end, different types of clearing elements arranged topermit the flow passage for the fuel to be cleared periodically, havealready been suggested, but it still remains essential to undertake acleaning action from time to time, by scraping the entire surface of thebase playing a part in the vaporization. This unavoidable operation isdifficult and dirty in all cases in the absence of a convenient means ofaccess to the bottom of the combustion pot and of removal of the scrapsseparated and broken over this base.

Another serious disadvantage of the known heating appliances ofthis kindis that the volume ofliquid fuel which accumulates in the bottom of thecombustion pot may remain considerable although it is limited by theconstant level valve, possibly of the order of several liters, owing tothe relatively great surfaceof the said bottom which may be of the orderof some square decimeters. When, after being turned off, the applianceloaded with a weight of fuel of this magnitude is relit, this may resultin overheating which can seriously impair the safety of the system as awhole, entailing grave risks of fire and of explosion of the appliance.

The main object of the present invention is to provide a liquid fuelheating appliance in which these disadvantages may be minimized oreliminated by providing for easy cleaning of the combustion pot, areduction in the maximum volume of fuel allowed to enter the burner, anda reduction of the surface exposed to soiling.

SUMMARY According to the present invention a liquid fuel heatingappliance comprises a liquid fuel burner comprising a combustion potwith perforate sidewalls, an elongate trough disposed laterally in thelower portion thereof, a feed pipe for feeding liquid fuel into thetrough, a constant level feed device for preventing the overflow of thefuel from the trough, there being an access passage integrally formedwith and generally aligned along the axis of the trough, the accesspassage extending through the sidewall ofthe pot and including anopening to provide straight line access along the entire length oftheelongate trough for removing debris therefrom.

By the appliance of the invention it is possible to clean the bottom ofthe combustion pot easily and without the risk of getting dirty, whilethe debris resulting from the cleaning can be easily collected in areceptacle under the access passage which preferably comprises a pipestub projecting from the wall of the combustion pot.

An extension of an access passage may be provided to form a fuelreception trough, channel or the like, the constant level valve beingarranged so that its control height is below the upper edge ofthetrough, whereby the fuel always remains enclosed therein.

This arrangement offers the very great advantage oflimiting the maximumvolume of liquid fuel liable to accumulate in the bottom of thecombustion pot, as well as limiting the wetted surface of the potbottom, and consequently the area of the surface likely to be soiled byincombustible wastes. At one stroke, it becomes even simpler to cleanoff these wastes, it being understood that although different forms maybe specified for the plan view structure of the fuel reception trough,these forms will preferably be selected so that there is access alongthe entire length of the wetted surface of the trough and a scrapingtool is easily inserted therein. The wetted surface of the trough is insuch a case a small fraction of the surface of the bottom of thecombustion pot.

By careful choice of the dimensions of the fuel reception trough it ispossible to secure a compromise reconciling two conditions, which arecontradictory at first sight, according to which the volume of fueldelivered by the constant level valve remains limited to a reasonableinitial value on the one hand, but on the other hand remains sufficientfor full-load operation of the appliance.

Contrary to the generally-accepted belief that the totality of thesurface of the combustion pot bottom is needed to ensure correctvaporization of the fuel in full-load operation, it is found that thedeliberately restricted surface of the fuel reception trough of theinvention is amply sufficient for a vaporization ofthis nature.

In a preferred embodiment of the invention an assembly is producedcombining a fuel reception trough and an access passage, comprising astamped component forming a trough placed astraddle on the lower rim ofa lateral opening formed for this purpose at the bottom of thecombustion pot, in conjunction with an openable cap or cowl capable ofcovering the part of the trough outside the pot.

This construction is particularly advantageous, in particular owing tothe fact that the inlet of the access passage normally covered by thecap is disposed wholly above the fuel reception trough; the applicationof seals to prevent leaks of liquid fuel can thus be omitted entirely,since the level of the liquid will always remain below the rim ofthetrough.

The access passage may also, on the other hand, advantageously serve thepurpose of ignition, which renders it possible to omit the pipe with aremovable lid specially incorporated for this purpose in appliances ofmany known appliances.

A lighting wick may be provided extending from the bottom of the fuelreception trough into the proximity of the coor- 'dinated accesspassage. This lighting wick preferably consists of a spout, chute or thelike, of very fine-meshed wire netting secured to the closing lid or capof the access passage abreast of an opening therein.

This spout, whose base is permanently immersed in the fuel, soaks thefuel up by capillarity, from loop to loop, to an appreciable height. Itis thus sufficient to allow a burning match or any other lighting deviceto enter the same to cause easy ignition of the burner; in point offact, this match is adequate to vaporize and then ignite the fuel,normally fuel oil, contained in the meshes of the spout. It is thuspossible to avoid the application ofa more volatile fuel, such asalcohol for example, and which is always dangerous to handle, for alighting action of this kind.

The trough may be in the form ofa stamping from relatively thin-gaugestainless steel sheet whose surface is polished at the inner side, atleast: experience shows that the adhesion of the solid combustion wastesis appreciably lessened on a metal surface thus polished ormirror-finished, thus evidently facilitating cleaning. Another advantageresides in the considerable reduction of thermal inertia, that is to sayof the metal mass in contact with the mass of liquid fuel, whichaccelerates and promotes the vaporizing process.

In this respect, the trough is preferably at a distance from the bottomof the combustion pot, so that it is not affected by cold air, which isequally favorable to the vaporizing process.

This vaporizing action may be promoted further still by a trough havinga bottom stepped on at least two levels; this arrangement renders itpossible to increase the useful wetted surface liable to come into playat high operational settings whilst additionally reducing the maximumvolume of fuel accumulated in the burner.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may bemore fully understood some embodiments in accordance therewith will nowbe described by way of example with reference to the accompanyingdrawings, in which:

FIG. I is a perspective view ofa combustion pot;

FIG. 2 is an elevation in part section showing the lower part of the potof FIG. I in a heating appliance;

FIG. 3 is a detail view in section along the line III-III of FIG. 2;

FIG. 4 is an elevation in part section of a construction comprising adistribution trough;

FIG. Sis a section along the line V-V ofFlG. 4;

FIG. 6 is a corresponding plan view in section along the line VI-VI ofFIG. 4;

FIG. 7 is an elevation of another embodiment;

FIG. 8 is a section along the line VIII-VIII of FIG. 7;

FIG. 9 is an elevation in part section showing the lower part ofa potequipped with a deflector;

FIG. 10 is a diagrammatic view in elevation and in part section of thelower part of another burner construction;

FIG. 11 is a partial view in axial section of a heating applianceequipped with another burner;

FIG. 12 is a partial external view of the burner of FIG. 11, looking inthe direction of the arrow XII of FIG. 13;

FIG. 13 is a longitudinal section of the assembly formed by the fuelreception trough ofthe burner of FIGS. 11 and I2 and by a cowlsupporting this trough; and

FIG. 14 is an exploded perspective view of the assembly of FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. I to 3, theseshow a burner pot I formed in conventional manner by a cylindrical sheetsteel vessel having in its lateral side perforations 2 for supply of airand equipped with one or more inner deflectors (not shown) for guidingthe flame and the comburant air. The cylindrical sleeve forming thebarrel of this pot is closed at the bottom by an inset cup-shaped base3. The pot thus formed is equipped with a radial access pipe 4 arrangedto be sealed off with a hermetic cover 5. The lower part of this accesspipe 4 is in the immediate vicinity of the bottom 3 of the combustionpot and is quasitangent to this bottom. In the middle part of the lengthand at the bottom of the access pipe 4, opens a joint 6 for connectionof the customary fuel feed pipe, connected to a constant level feedvalve (not shown), this joint forming an inlet substantially tangentialto the inner wall of the pipe. On the other hand, a pipe 7 is radiallydisposed relative to the pipe 4, normally closed off by a removable lid8 and in manner known per se serving the purpose of an access and aninlet for additional air for ignition. The pipe 4 thus arranged is inalignment with a door 9 when the combustion pot is installed in theheating jacket or case 10 ofa heating appliance.

The access pipe 4 which is in alignment with and in extension of thebottom 3 of the combustion pot, is of sufficient size, when the door 9is opened and the cap 5 has been removed, to allow passage for a toolfor cleaning the bottom 3 by scraping, as shown dash-dotted at N in FIG.2. Owing to the positioning of the pipe 4 in direct proximity to thebottom 3, the wastes separated therefrom may easily be extracted throughthis pipe 4, and owing to the projection of this pipe from the side ofthe combustion pot, these wastes may easily be collected in a pan or anyother appropriate receptacle placed below the outlet of the pipe 4.

In the construction shown in FIGS. 4 to 6, there is a pot 11 having aninset bottom I3 with an access pipe 14 possessing a hermetic cover 15, afuel feed 16, and an igniting pipe 17. The access pipe 14, in this case,is slightly raised and slopes above the bottom 13 and is extended by afuel reception element 20 in the form ofa trough arranged, for exampleas in FIG. 6 in the form ofa tube section closed at its extremity 21 andopen at 22 at the top by removal of a fraction of the ordervof a quarterof its circumference, for example. I

This trough 20 is preferably secured at a distance from the bottom 13,without contact with the same. The fuel feed 16 being supplied inconventional manner by a pipe 18 equipped with a constant level valve19, the appliance is arranged so that the level H of the liquid fuel tobe set by this valve is below the lowest point of the upper rim ofthetrough 20.

The section and length of this trough 20, which in this case extends inalignment with a diameter of the bottom of the combustion pot whenviewed in plan, are determined so that the volume defined by the level Hand the wetted surface of the trough 20 establishes a satisfactorybalance between the vaporizing surface on the one hand the volume ofliquid fuel and the quantity of comburant air, on the other hand.

The wetted surface of the trough 20 thus represents no more than alimited fraction of the surface of the base of the combustion pot.

FIGS. 7 and 8 show another form of embodiment of a fuel reception troughat the bottom ofa pot 11; in this case, it is integral with the lowerinset part 23 of the combustion pot by stamping into the base thereof achannel or trough 25 direction substantially diametrically across thebottom'and having a semicircular cross section in which the diameterincreases with distance from the access pipe 24. The nominal level H, inthis case, is still below the upper edge of the trough thus formed, thatis to say below the actual bottom ofthe pot.

The trough thus punched out may comprise an initial portion arranged inextension of the access pipe and a bifurcation into two branches, thewhole forming a Y-shaped pattern in plan view. Or the trough maycomprise an initial portion in the extension of the access pipe 24 and apart widened into the shape ofa bulb occupying a portion of the bottomof the pot.

At all events, the different parts of the fuel reception troughpreferably remain directly visible from the inlet of the pipe 24, andthus directly accessible by a scraper or other appropriate tool forperiodical cleaning operations by removal of the more or less coked fuelwastes.

In all instances moreover, the wetted surface of the fuel receptiontrough should preferably amount to no more than a limited fraction ofthe surface of the combustion pot. This fraction should be smaller thanhalf and preferably between one tenth and one third. In practice, it ispreferably between one eighth and a fifth.

FIG. 9 shows an arrangement in which the trough 20 is disposed above thebase as in the embodiments of FIGS. 4 to 6, but such a trough may be ofany other form, of a deflector 31 advantageously consisting of aninverted dinner plateshape having in its lateral side a circular row ofopenings 32 for passage of air and providing at its circumference aperipheral passage 33. In operation, the deflector thus formed, havingits upper face exposed to the radiation of the flames, assures uniformand appropriately maintained heating of the mass of liquid contained inthe trough 20 whilst allowing of uniform vaporization of this mass underprotection from turbulences which could occur in the area of the flames.

The supply of comburant air is assured by the circular row of openings32 and the combustible mixture thus formed is channelled, as indicatedby the arrows, along the wall of the pot, thus assuring a regular supplyof secondary air to the combustion through the lateral perforations inthe cylindrical steel vessel (FIG. 1).

Finally, with reference to FIGS. 10 to 14, forms of embodiment of theinvention will be described, characterized by the fuel reception troughon the one hand, and the access passage on the other hand, being wroughtin the form of an unitary assembly.

In FIG. 10, the lower part of the combustion pot (41 in FIG. comprises alateral opening 42 of generally rectangular shape for example, and atrough 43 formed by a stamping of stainless steel is placed astraddle onthe lower edge of the opening, so that a terminal portion 44 of thistrough remains outside the pot. The trough, which is plan view has anclongated rectangular shape, is enframed by a plane flange 5 extendingthroughout its periphery. Within the frame is formed a bowl or pan intwo parts 4647 ofdifferent depths formed by a base stepped on twodifferent levels, the lower level being closer to the terminal portion44 on a side of which portion is arranged the union 48 for connection ofthe fuel feed pipe.

As apparent from FIG. 10, trough 43 is disposed with a moderate inwardand downward slope so that the scheduled level H of the constant levelvalve 19 is slightly above the transition crest 50 between the portions46 and 47 of the pan.

In the area of the opening 42, the trough is topped by a transverse dome51 which matches the rest of the outline of the said opening. Incombination with the dome, a lid 52 articulated by a hinge 53 on theouter edge of the dome, is arranged to close the remainder of theterminal part 44 of the trough which is outside the pot and not coveredby the arched portion 51. An opening, which is not apparent from FIG.10, is formed in the upper face of the lid 52 and a flap is employed formore or less complete closure thereof.

It is apparent that, by tipping the lid 52 upwards, a particularlyconvenient access is available, providing a direct sight of the whole ofthe pan formed by the trough 43. For lighting purposes, this accessmeans may be employed or the opening in the lid 52 may be used for thispurpose. At all events, direct visibility is available of the fuelinflow through the union 48 and the presence and size of the sheet ofliquid fuel to be ignited can be assessed. In operation, it remainspossible to establish and maintain an inflow of air with an adjustablerate of flow, through the opening in the lid 52, by placing the flapcoordinated with this opening in the appropriate position.

The stepped arrangement of the bottom renders it possible to increasethe vaporizing surface whilst limiting the maximum volume of the liquidmass to an even lower value than in the preceding forms of embodiment.The vaporizing process is greatly facilitated, on the one hand thanks tothe reduced thermal inertia of the distribution trough 43 which mayadvantageously be made of thin-gauge steel and preferably of stainlesssteel, ofa thickness of5 to 6 tenths of 1 mm., for example. This sheetmay be polished or mirror-finished on its inner surface at least:experience shows that this arrangement considerably reduces the adhesionof solid deposits and consequently facilitates their removal.

The principal advantage of this form of embodiment appears however toreside in the fact that the removable lid 52 of the access passagewholly remains distinctly above the highest position of the level H ofliquid, thus eliminating any risk of overflow, leakage or seepage of theliquid fuel without having to use any kind of plastic seals.

The hinged lid 52 may be replaced by a lid slidingly arranged on thetrough 43, on its flange 45.

In FIG. 11 at 41 is a combustion pot in which is cut a lateral opening42 ofgenerally rectangular shaped, and a trough 63 is placed straddlingthe lower edge of this opening. This trough is borne by a cowling or cap64 equipped with a peripheral flange 65 by which it is secured to thecombustion pct 41, around the opening 42 thereof.

The trough 63 consists of a stainless steel sheet stamping, for example;its bottom is in the form of a very widely open Vee, that is to say thatit has two plane sides 67, 68 converging at a low slope towards a commonlower inverted crest 69.

By brackets or lugs 70, this trough 63 has arranged above it an annulardeflector 71 in a manner known per se, the deflector could be carried bythe combustion pot 41 itself, but its fastening to the distributiontrough 63 itself results in forming an assembly whose production andinstallation are more economical.

The cap 64 is formed by a frustopyramidal element 72 (FIGS. 12 and 13),having a peripheral flange 65; this element 72 is extended by acylindrical section 73 having a flange at its end forming a rectangularopening 74 forming the access passage arranged for the insertion ofacleaning tool.

On this section 73 is engaged a removable cover 75 with theinterposition ofa sealing joint 76.

The cover 75 is pierced by an opening 77. Internally, by two sections78, 79, it carries a sloping ignition chute whose lower extremity isclose to the bottom of the trough 63 and whose upper extremity is closeto the lid or cover 75, in alignment with its opening 77. This chute 80consists of metal wirenetting with very flne meshes.

Externally, the cover 75 carries a plate 81 forming, with the cover, aseat in which a shutter 82 is arranged to pivot around a pin 83. Thisshutter controls the opening 77 of the cover 75; it has an operating tab84 equipped at either side with insulating pads 85, 86 allowing it to begrasped; the flap 82 moreover has resiliently deformable strips 87formed by cutting and appropriately deforming the panel from which itextends, the strips by means of the friction against the flange 81assuring correct retention of the flap or shutter 82 irrespective of itsposition.

The flange 81 is provided with an opening 88 aligned with the opening 77of the cover 75 and laterally has two pegs 90, 91 on which are hingedtwo hooks 92, 93 interconnected by a shared handling grip 94.

These hooks 92, 93 are intended to cooperate with lugs 95, 96 carriedlaterally by the barrel 72 of the cap 64 for locking the removable cover75 on the cap.

The trough 63 and the cap 64 moreover possess openings 97, 98 inalignment for securing a union (not shown) for connection of the fuelpipe. This feed occurs through a constant level valve 19 which, aspreviously, is arranged in such manner that the sheet of fuel in thetrough 63 is limited to the level II (FIG. 11), this level H being lowerthan the top section of the trough.

The openings 77 and 88 which are controlled by the shutter 82, reader itpossible to insert an igniting means such as an ignited match or thelike, on the one hand, the igniting means being slipped into the chute80, and on the other hand, allow of providing a supply of secondary aircontrolled by the shutter 82, particularly during the igniting action.

It is possible to equip one and the same combustion pot with severalfuel reception troughs, which may be identical or not, these troughs forexample being disposed in a star-shaped pattern, especially in the caseof a cylindrical combustion pot having a circular base, or else disposedparallel to each other at equal distances or not, specifically to form alinear burner.

I claim:

I. A liquid fuel burner comprising a combustion pot with perforatesidewalls, an elongate trough disposed laterally in the lower portionthereof and having a width substantially less than the width of saidlower portion of said pot, a feed pipe for feeding liquid fuel into thetrough, a constant level feed device for preventing the overflow of thefuel from the trough, means defining an access passage integrally formedwith and generally aligned along the axis of the trough, the accesspassage extending through the sidewall of the pot and including aremovable cover over an opening to provide straight line access alongthe entire length of the elongate trough for removing debris therefrom.

2. A burner according to claim 1, said opening extending most ofthewidth ofthe trough.

3. A burner as claimed in claim I, the bottom of the trough beingsmoothly inclined up to said opening to facilitate the removal ofdebrisfrom said trough through said opening.

4. A burner according to claim 1 wherein the fuel wetted surface area ofsaid trough is a fraction of the cross section of the lower portion ofthe pot.

5. A burner according to claim 1 wherein the whole of said fuel wettedsurface of said trough is visible from said access and can be reached bya scraping tool inserted into said passage.

6. A burner according to claim 1 wherein said trough is a cavity stampedinto said pot bottom.

7. A burner according to claim 1 wherein said trough is an element insetin a sidewall of said pot.

8. A burner according to claim 1 wherein the whole of said trough isdisposed at a distance from said pot bottom.

9. A burner according to claim 8 wherein said trough has a stepped baseproviding two levels of different heights with respect to said potbottom.

10. A burner according to claim 1 wherein the bottom of said trough hasa cross section of an oblique angle V.

11. A burner according to claim 1 wherein said trough is of polishedstainless steel sheet.

12. A burner according to claim 1 wherein said trough has a deflectordisposed above it and shaped to deflect the mass of vaporized fuel closeto the interior part of said pot, said deflector being shaped as aninverted dinner-plate having a peripheral flow passage for flow risingalong the inner side of said pot.

13. A liquid fuel burner as claimed in claim 1 wherein said trough iscoordinated with an ignition wick extending from the bottom of saidtrough to a point close to said passage.

14. A burner according to claim 13 wherein said wick is a sloping chutepierced by a network of close set narrow orifices.

15. A burner according to claim 13 wherein said chute is formed by finemesh wire netting.

16. A burner according to claim 13 wherein said wick is secured to saidcover.

17. A liquid fuel burner comprising a combustion pot having perforationsin the side thereof, a constant level feed valve connected to said potby a feed pipe, and a fuel trough in said pot and connected to said pipeand to a passage giving access to said pot bottom, said valve beingdisposed with the controlled fuel level below the upper edge of saidtrough thereby enclosing the fuel therein, the lower part of said potbeing pierced by an opening the lower edge of which is straddled by saidtrough, and a cowl covering the part of said trough outside said pot. I

18. A burner according to claim 17 wherein a transverse dome surmountssaid trough in the area of said pot opening and matches the shape ofsaid opening, said cowl being hinged to said dome.

19. A burner according to claim 17 wherein said cowl is slidable withrespect to said trough.

20. A burner according to claim 17 wherein said cowl has an air inletopening and means to vary the area of said openmg.

21. A burner according to claim 17 wherein said trough is supported by acowling having its periphery secured to said pot around said openingtherein and having an opening closed by said cowl.

22. A burner according to claim 17 wherein said trough is supported by acowling having its periphery secured to said pot around said openingtherein and having an opening closed by said cowl, said cowlingcomprising an extension round said opening therein, the coordinatedcover being filled to said extension and securable thereto by twolateral hooks solid with an operating member.

23. A burner according to claim 17 wherein said coordinated cover has anair inlet opening with a shutter displaceable between said cover and aflange thereon, said shutter having elastically deformable projectingstrips maintaining said shutter in position by friction.

1. A liquid fuel burner comprising a combustion pot with perforate sidewalls, an elongate trough disposed laterally in the lower portion thereof and having a width substantially less than the width of said lower portion of said pot, a feed pipe for feeding liquid fuel into the trough, a constant level feed device for preventing the overflow of the fuel from the trough, means defining an access passage integrally formed with and generally aligned along the axis of the trough, the access passage extending through the sidewall of the pot and including a removable cover over an opening to provide straight line access along the entire length of the elongate trough for removing debris therefrom.
 2. A burner according to claim 1, said opening extending most of the width of the trough.
 3. A burner as claimed in claim 1, the bottom of the trough being smoothly inclined up to said opening to facilitate the removal of debris from said trough through said opening.
 4. A burner according to claim 1 wherein the fuel wetted surface area of said trough is a fraction of the cross section of the lower portion of the pot.
 5. A burner according to claim 1 wherein the whole of said fuel wetted surface of said trough is visible from said access and can be reached by a scraping tool inserted into said passage.
 6. A burner according to claim 1 wherein said trough is a cavity stamped into said pot bottom.
 7. A burner according to claim 1 wherein said trough is an element inset in a sidewall of said pot.
 8. A burner according to claim 1 wherein the whole of said trough is disposed at a distance from said pot bottom.
 9. A burner according to claim 8 wherein said trough has a stepped base providing two levels of different heights with respect to said pot bottom.
 10. A burner according to claim 1 wherein the bottom of said trough has a cross section of an oblique angle V.
 11. A burner according to claim 1 wherein said trough is of polished stainless steel sheet.
 12. A burner according to claim 1 wherein said trough has a deflector disposed above it and shaped to deflect the mass of vaporized fuel close to the interior part of said pot, said deflector being shaped as an inverted dinner-plate having a peripheral flow passage for flow rising along the inner side of said pot.
 13. A liquid fuel burner as claimed in claim 1 wherein said trough is coordinated with an ignition wick extending from the bottom of said trough to a point close to said passage.
 14. A burner according to claim 13 wherein said wick is a sloping chute pierced by a network of close set narrow orifices.
 15. A burner according to claim 13 wherein said chute is formed by fine mesh wire netting.
 16. A burner according to claim 13 wherein said wick is secured to said cover.
 17. A liquid fuel burner comprising a combustion pot having perforations in the side thereof, a constant level feed valve connected to said pot by a feed pipe, and a fuel trough in said pot and connected to said pipe and to a passage giving access to said pot bottom, said valve being disposed with the controlled fuel level below the upper edge of said trough thereby enclosing the fuel therein, the lower part of said pot being pierced by an opening the lower edge of which is straddled by said trough, and a cowl covering the part of said trough outside said pot.
 18. A burner according to claim 17 wherein a transverse dome surmounts said trough in the area of said pot opening and matches the shape of said opening, said cowl being hinged to said dome.
 19. A burner according to claim 17 wherein said cowl is slIdable with respect to said trough.
 20. A burner according to claim 17 wherein said cowl has an air inlet opening and means to vary the area of said opening.
 21. A burner according to claim 17 wherein said trough is supported by a cowling having its periphery secured to said pot around said opening therein and having an opening closed by said cowl.
 22. A burner according to claim 17 wherein said trough is supported by a cowling having its periphery secured to said pot around said opening therein and having an opening closed by said cowl, said cowling comprising an extension round said opening therein, the coordinated cover being filled to said extension and securable thereto by two lateral hooks solid with an operating member.
 23. A burner according to claim 17 wherein said coordinated cover has an air inlet opening with a shutter displaceable between said cover and a flange thereon, said shutter having elastically deformable projecting strips maintaining said shutter in position by friction. 